FIG. 1 is a systematic block diagram showing an LED (light emitting diode) backlight module provided in an existing skill. As shown in FIG. 1, the LED backlight module includes a rectifier filter module, a DC-DC converting module, a high-frequency rectifier filter module, a boost circuit 101, an LED load, and an output feedback module. In the existing LED backlight module, an alternating current U_vin of 220V passes through the rectifier filter module, the DC-DC converting module, and the high-frequency rectifier filter module, and then is outputted as a first power source U1 and a second power source U2. Generally, the second power source U2 is used to drive a chip board/CB and the first power source U1 is used to drive the LED load.
Usually, the existing boost circuit is required to cooperate with an LED driving chip to drive the LED load. FIG. 2 is a schematic diagram showing the existing boost circuit 101 and the LED load. As shown in FIG. 2, the booster circuit 101 is used to pull up the first power source U1 and then supply it to the LED load. The booster circuit 101 includes an LED driving chip M1 and a switch Q1. The first power source U1 also provides a driving voltage for the LED driving chip M1. However, the range of the driving voltage is too wide such that the LED driving chip M1 works under a lower voltage. The LED driving chip M1 starts to work when the first power source U1 is low in voltage such that the current flowing through the switch Q1 is too large, causing a damage of the switch Q1 and reducing the reliability of the LED driving circuit.
Therefore, there is a need to provide a protection circuit and an LED driving circuit for solving the problems caused in the existing skills.